This invention relates to covered grain piles and, more particularly to cover-on-first grain piles, that is, piles wherein the grain is introduced under a previously positioned cover. In one aspect the invention is concerned with contemporary storage facilities wherein grain is introduced under a flexible cover and formed into a pile as large as one-million bushels, or more. A typical example is disclosed in Wolstenholme U.S. Pat. No. 4,493,248.
As taught in the Wolstenholme patent, triangularly shaped sections of canvas are laid out surrounding a tower situated inside a retaining wall and are edgewise joined to define a flexible cover. The apices of the triangular canvas sections are joined to a lifting ring and are hoisted up the tower to a predetermined height. This causes the cover to pull saggingly inward. The grain which is to be stored is transported by conveyor to the top of the tower and then poured downwardly through the center of the tower to spaced outlets. It exits the tower through those outlets and forms a pile which lifts and spreads the cover. Grain spoilage is avoided during storage by an aeration technique using a fan mounted at the top of the tower. The fan is operated to pull a flow of cooling air through perforations in the retaining wall, thence through the grain pile and finally through perforations in the tower. The air is then exhausted to the atmosphere.
The Wolstenholme patent represents a substantial improvement over cover-on-after systems, because it avoids labor intensive manual spreading of the cover on top of the grain. It also avoids risk of water damage by keeping the grain covered throughout the fill. Yet there remain three problems for which a solution is desired. First there is a rather considerable expense involved in building the tower and erecting elevated conveyors. Secondly, if heavy weather occurs during a fill, the cover must be lowered to a sheltered position against the grain. This avoids wind damage but interrupts filling. Thirdly, the grain suffers damage from impact against conveyor buckets during elevation, against downspouts during a high velocity fall and against the base of an empty or partially empty storage facility at the end of the fall.
In a second aspect the invention is concerned with traditional grain storage facilities equipped with self-supporting covers (roofs). Such facilities generally have side walls reaching higher than the maximum height of the grain stored therein. Typical examples are concrete silos and steel storage buildings. Heretofore traditional grain storage facilities have been filled by conveying the grain to an elevated location and then dropping it inside the facility. Again, there is a certain expense factor associated with elevated conveying. Furthermore, as the grain falls into the storage facility it raises considerable dust, which creates a risk of explosion. There is a need for a method of forming a grain pile which eliminates these concerns.